Multi-layer filtration device

ABSTRACT

A filter device assembly and a method of using such a device to capture and remove embolic material from a body lumen or blood vessel are provided. The filter device assembly generally includes a structure having a collapsed state and an expanded state with first, second, and optionally N additional filter members circumferentially attached thereto. Each filter member forms an annulus chamber with the first filter member having porosity P 1 ; the second filter member circumferentially having porosity P 2 ; and the N additional filter members each having porosity [P 3  . . . P (2+N )]. The magnitude of the porosity for the first, second, and N additional filter members follows the relationship P 1 &gt;[P 3 &gt;. . . &gt;P (2+N )]&gt;P 2 . The first, second, and N additional filter portions are configured in the expanded state to allow blood to flow there through and to capture emboli in the annulus chambers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and claims the benefit of priority toSer. No. 13/211,409, filed on Aug. 17, 2011, now U.S. Pat. No. 8,617,200entitled “MULTI-LAYER FILTRATION DEVICE,” the entire contents of whichis incorporated herein by reference.

FIELD

This disclosure relates generally to medical devices. More specifically,this disclosure relates to a filter device assembly and a method ofusing such a device to capture and remove embolic material from a bodylumen or vessel.

BACKGROUND

Since the kidneys filter or remove waste products and excess fluids fromthe blood, approximately one-third of the blood delivered from the heartflows through the kidneys. This flow of blood also allows the kidneys toplay a major role in regulating the blood pressure in a person. When thebuild-up of plaque (atherosclerosis), as well as other abnormalitiesthat may occur in the renal artery, cause enough narrowing or blockageof the artery such that the supply of blood to the kidney is reduced,the risk of kidney damage becomes very high. If this condition, i.e.,renal artery stenosis, is left untreated it can lead to high bloodpressure, reduced functioning of the kidneys, and/or even kidneyfailure.

A standard procedure used in the treatment of endovascular diseases andabnormalities is the placement of medical devices, such as emboliccoils, stents, and dilation balloons, among others, at a desired ortargeted site within a patient. The delivery of such a medical devicehas typically been accomplished by a variety of means, including the useof a catheter through which the device travels for deployment to thetargeted site. These medical devices usually have a contracted shapethat allows them to pass through the lumen of the catheter and anexpanded shape for engagement with the body vessel that occurs afterbeing deployed at the targeted site.

A renal stent is an example of such a medical device. The stent acts asa scaffold, by keeping the artery stretched open and maintainingadequate blood flow through the vessel. However, because renal arterystents are exposed to the flow of blood, they may facilitate theformation of clots until the stent becomes covered with tissue from thebody. Various medications are usually given to the patient at this timeto prevent the occurrence of thrombosis, i.e., the formation of a bloodclot.

In order to increase the safety of using stents and other devices in thevasculature of a patient, embolic protection devices have been developedas a means to capture blood clots and other embolic particles that maybecome dislodged from a stenosis or the treatment thereof. Such devicesmay be deployed within a vessel at a site distal, e.g., downstream, tothe stenosis before the treatment takes place. In a deployedconfiguration, the embolic protection device is intended to act as afilter that allows blood to pass through, but traps any embolicparticles, such as atherosclenotic plaque or a thrombus, attempting toflow therewith.

Multiple issues exist with the design, manufacturing, and use ofexisting filter devices. Among these issues is the desirability undercertain circumstances to deploy the filter device from the proximal sideof the stenosed region. Therefore, the profile of the filtering deviceshould be smaller than the opening through the stenosed region. Anotherissue, among many, resides in the filter portion being susceptible tobecoming clogged or occluded during treatment, thereby, reducing theblood flow through the blood vessel. Accordingly, there is a continualdesire to provide improved devices and methods for capturing emboliwithin a blood vessel. A filter device that provides distal protectionduring a procedure that has the potential to produce emboli withoutsubstantially restricting blood flow through the vessel would bebeneficial.

SUMMARY

In satisfying the above need, as well as overcoming the enumerateddrawbacks and other limitations of the related art, the presentdisclosure generally provides a filter device assembly for capturingembolic particles in a blood vessel. The device comprises a structurethat has a predetermined shape with a distal portion, proximal portion,and optionally a middle portion. The structure is configured to movebetween an expanded state for engagement with the blood vessel and acollapsed state for delivery and retrieval. The structure of the filterdevice in its expanded state has a substantially cylindrical shape.

The filter device assembly further includes a first filter member, asecond filter member, and optionally N additional filter memberscircumferentially attached to the structure with each filter memberforming an annulus chamber. The first filter member exhibits porosity,P₁, while the second and filter member exhibits porosity, P₂. Theoptional N additional filter members when present each exhibit aporosity, [P₃ . . . P_((2+N))]. The porosity associated with each filtermember follows the order P₁>[P₃> . . . >P_((2+N))]>P₂. The first,second, and N additional filter members are configured in the expandedstate to allow blood to flow there through and to capture emboli in theannulus chambers.

According to one aspect of the present disclosure, the porosity P₁ is atleast about 150 micrometers and the porosity P₂ is equal to or less thanabout 50 micrometers. The porosity of each additional filter member, [P₃. . . P_((2+N))], is greater than about 50 micrometers and less thanabout 150 micrometers.

According to another aspect of the present disclosure a method forproviding embolic protection during the treatment of a stenosis,occlusion, lesion, or other defect in a body vessel is provided. Thismethod generally comprises the steps of introducing a catheter into thebody vessel and locating the end of said catheter proximate to a targetsite. A filter device assembly is then placed into the catheter. Thisfilter device assembly has the configuration and design as describedherein. The filter device is moved through the catheter and deployed tothe targeted site in a collapsed state. The targeted site is generallydownstream or past the stenosis, occlusion, lesion, or other defect inthe body vessel. Once deployed in the body vessel, the filter device isallowed to move from its collapsed state to an expanded state. After thefilter device assembly has reached its expanded state, the stenosis,occlusion, lesion, or other defect in the body vessel may be treated.Such treatment may include the deployment of a stent or other medicaldevice, chemical dissolution, or mechanical thrombolysis, among others.The method may also comprise the step of withdrawing the catheter fromthe body vessel.

During the use of the filter device assembly, the first filter portionallows emboli having a diameter larger than porosity, P₁, to be capturedand emboli having a diameter smaller than porosity, P₁, to pass therethrough along with the flow of blood to the adjacent filter portion.Similarly, the second filter portion allows emboli having a diameterlarger than porosity, P₂, to be captured and emboli having a diametersmaller than the porosity, P₂, to pass through along with the flow ofblood. Each of the N additional filter portions allows emboli having adiameter larger than the corresponding porosity, [P₃ . . . P_((2+N))],to be captured and emboli having a diameter smaller than the porosity,[P₃ . . . P_((2+N))], to pass through along with the flow of blood tothe adjacent filter portion.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1A is a cross-sectional, longitudinal view of a body vessel showinga perspective view of a multi-layer filter device assembly deployedaccording to one aspect of the present disclosure;

FIG. 1B is a close-up view of the center rod coupling the first andsecond sections together in the multi-layer filter device of FIG. 1A;

FIG. 1C is a perspective view of the frame surrounding the multi-layerfilter device according to another aspect of the present disclosure;

FIG. 2 is a schematic representation of a method of deploying a filterdevice assembly into a vasculature of a patient; the filter deviceassembly being made according to the teachings of the presentdisclosure;

FIG. 3A is a cross-sectional, longitudinal view of a body vessel inwhich a catheter is positioned downstream from an obstruction accordingto one aspect of the present disclosure;

FIG. 3B is a cross-sectional, longitudinal view of the body vessel ofFIG. 3A in which the filter device assembly is being deployed in itscollapsed state with subsequent transitioning to its expanded state;

FIG. 3C is a cross-sectional, longitudinal view of the body vessel ofFIG. 3B in which a stent is fully deployed;

FIG. 3D is a cross sectional, longitudinal view of the body vessel ofFIG. 3C in which treatment of the obstruction is being accomplished viathe insertion of a stent according to one aspect of the presentdisclosure;

FIG. 3E is a cross-sectional, longitudinal view of the body vessel ofFIG. 3C in which treatment of the obstruction is being accomplished viathe insertion of a balloon according to another aspect of the presentdisclosure; and

FIG. 3F is a cross-sectional, longitudinal view of the body vessel ofFIG. 3C in which the multi-layer filter device assembly is withdrawnafter the treatment of the obstruction according to yet another aspectof the present disclosure.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is in no wayintended to limit the present disclosure or its application or uses. Itshould be understood that throughout the description and drawings,corresponding reference numerals indicate like or corresponding partsand features.

The present disclosure generally provides a filter device assembly and amethod of using such a device to capture and remove embolic materialfrom a body lumen or vessel. As a result, the filter device assembly ofthe present disclosure may be used to improve the circulation of bloodthrough the body lumen and to reduce the chance of clot oratherosclenotic material related issues, such as embolization at theanterior end of the kidney or with other organs. Although the filterdevice assembly is depicted in the Figures and described herein toinclude three filter members, one skilled in the art will understandthat the filter device assembly may include any desired number of filtermembers (e.g., 2, 3, 4, 5, etc.) without exceeding the scope of thepresent disclosure; provided that the number of filter members is atleast two filter members. The desired number of filter members presentin the filter device assembly is predetermined by the intended use ormedical application for the device assembly.

Referring to FIG. 1A, the filter device assembly 1 as deployed in a bodyvessel 5 according to one aspect of the present disclosure, comprises astructure 5 having a frame 10 with a predetermined shape; the frameincludes a distal 11 portion, a proximal 13 portion, and an optionalmiddle 12 portion. In this example, the filter device assembly 1 ispositioned to capture embolic material or thrombi carried by the bloodflowing 30 through the artery or body vessel 7 with filter members 15,20, 25 being fully deployed adjacent to the vessel wall 17. The proximalend of the structure 5 may be coupled to a guide wire 22 or include ahook or other means which can be used to couple to a guide wire 22. Thedistal end of the structure 5 is preferably open through the use of ahollow hub 21 to allow the passage of a guide wire. The overallstructure 5 is configured to move between an expanded state forengagement of the frame 10 with the wall 17 of the body vessel 7 and acollapsed state for delivery and retrieval. A part of the frame 10 mayalso act as struts 26 that provide support for each filter member 15,20, 25 in the assembly's 1 expanded state.

The distal 11, optional middle 12, and proximal 13 portions of thefilter device assembly 1 may be coupled through any means known to oneskilled in the art. One example of coupling the proximal portion 13 todistal portion 11, or to the middle portion 12 and the middle portion 12to the distal portion 11 when the optional middle portion 12 is present,includes the use of a shaft 3. Referring now to FIG. 1B, the shaft 3 maybe hollow or solid and contain a solid, unperforated center section 2along with proximal 23 and distal 24 perforated sections. The proximalperforated section 23 may be used as struts for supporting the filtermembers 15, 20, 25 when they are in the expanded state.

Referring once again to FIG. 1A, a first filter member 15 has a proximalpart and a distal part, the proximal part is circumferentially attachedto the proximal portion 13 of the frame 10 with the distal part of thefilter member 15 being coupled to a shaft 3. Similarly, a second filtermember 20 has proximal part and distal part, the proximal part iscircumferentially attached to the distal portion 11 of the frame 10. Thedistal part of the second filter member 20 being coupled to the end hub21. The first filter member 15 forms a first annulus chamber within thedevice 1 having a first porosity level, P₁. The second filter member 20forms a second annulus chamber within the device 1 having a secondporosity level, P₂. The filter portions 15, 20, 25 are configured in theexpanded state to allow blood to flow 30 there through and to captureemboli in the annulus chambers. The magnitude of the porosity for thefirst and second filter members follows the relationship P₁>P₂.

The filter device assembly 1 may further comprise N additional filtermembers, wherein N is an integer greater than or equal to one. Each ofthe N additional filter members has a proximal part and a distal part,the proximal part circumferentially attached to the middle portion ofthe frame 10; the distal part closed such that each N additional filtermember forms an annulus chamber having a porosity [P₃> . . .>P_((2+N))]. As shown in FIG. 1A, when N=1, a third filter member 25 ispresent in the filter device assembly 1 forming a third annulus chamberwithin the device having a porosity level, P₃. The magnitude of theporosity for each of the N additional filter members follows therelationship P₁>[P₃> . . . >P_((2+N))]>P₂. The distal part of eachadditional filter member may be coupled to the shaft 3.

The porosity of each filter member 15, 20, 25 is given by therelationship P₁>[P₃> . . . >P_((2+N))]>P₂. According to one aspect ofthe present disclosure, porosity P₁ is at least about 150 micrometers,while porosity P₂ is equal to or less than about 50 micrometers. Theporosity, [P₃ . . . P_((2+N))], of each additional filter member may beany value that is between P₁ and P₂. In other words, the porosity [P₃ .. . P_((2+N))] may range between about 50 to about 150 micrometers. Inthe specific example described in FIG. 1A, a third filter member 25having a porosity of about 100 micrometers is preferred. According toanother aspect of the present disclosure, the porosity P₂ should belarger than about 7.5 micrometers in order not to restrict the flow ofred and/or white blood cells through the filter device 1.

The number of filter members present in the filter device assembly 1 ispredetermined depending upon the expected or intended application or usefor the device assembly 1. For example, a filter device assembly 1having three filter members is preferable for use in the renal artery.Similarly, a filter device assembly 1 having two filter chambers mayfind use in arteries below the knee, while a device assembly with fouror five filter members may find use in other arteries, such as incarotid, superficial femoral, or iliac systems.

Still referring to FIG. 1A, according to another aspect of the presentdisclosure, the structure 5 may be configured to provide the body of thefilter device assembly 1 with a substantially cylindrical shape in itsexpanded state. The length of the filter device assembly 1 may varydepending upon the intended application. For example, when used in therenal artery, the length of the filter device assembly is preferably onthe order of about 1.5 centimeters. In the expanded state, the shape ofthe filter device assembly 1 will define an interior volume thatprovides an entrapment region for capturing and holding embolicmaterial. The spacing within the frame 10 of the structure 5 can bepredetermined and configured for use in a given application. Referringnow to FIG. 1C, various parts of the frame 10 may be coupled through theuse of support wires 27 angled in a predetermined manner to provide thestrength and support desired for the structure 5 when in either thecollapsed or expanded states. The frame 10 may include struts 23 andother support media arranged in a manner that creates very littleresistance to blood flow through the body lumen or vessel. The filterdevice assembly 1 is preferably configured to be collapsible into asmaller cross-sectional profile for facilitating its delivery to andretrieval from the targeted treatment site. The filter device assembly 1in its expanded state interacts with the inner walls of the body lumenor vessel in order to secure the device in place and ensure that bloodflows through the interior volume of the device 1.

The structure 5 of the filter device assembly 1 may comprise any metal,metal alloy, polymeric material, and/or combination thereof known to oneskilled-in-the-art. According to one aspect of the present disclosure,the structure 5 of the filter device assembly 1 may comprise asuperelastic material, stainless steel wire, Nitinol,cobalt-chromium-nickel-molybdenum-iron alloy, or cobalt chrome-alloy orany other material suitable for use in a filter device that allows forthe transitioning between an expanded state and a collapsed state, aswell as extended durability and flexibility. According to another aspectof this disclosure, at least a portion of the filter device assembly 1may optionally have one or more surface treatments applied thereto,including but not limited to coatings, machining, texturing,electropolishing, media blasting, and chemical etching.

The filter material used in the first 15, second 20, third 25 members,and any other additional filter members may be formed from any suitablematerial known to one skilled-in-the-art to be used in capturing ortrapping embolic particles from a flowing blood stream. The selectedmaterial may be independently selected for use in the first 15, second20, third 25, and other additional filter members. The material selectedfor use with each member will exhibit the porosity level desired forthat member. In one embodiment, the filter material may be made at leastpartially of a non-woven material, knits, braids, or a textilecomposite, including, but not limited to, a woven fabric, a moldedpolymer, a polymer film, or a combination thereof. Such fabrics andpolymers may include but not be limited to nylon;poly(tetrafluoroethylene), such as Teflon® (DuPont de Nemours);polyethylene, such as Dyneema® (DSM Dyneema), polyester, such as Dacron®(Invista, Koch Industries), and mixtures or combinations thereof. Thefilter material may also include a biological graft material, such assmall intestinal submucosa (SIS) or another extracellular material(ECM). The graft materials may be cross-linked for stability if desired.

Another objective of the present disclosure is to provide a method 100of using the filter device assembly 1 described herein at a targetedsite in the vasculature 5 of a patient. FIG. 2 depicts an example of amethod 100 that uses the filter device assembly 1 described herein. Thismethod 100 generally comprises introducing 105 a catheter into the bodyvessel of a patient and positioning the distal end of said catheter at adesired or targeted site. The aforementioned filter device assembly 1 isthen placed 110 into the catheter in a collapsed state. When desirable,the filter device assembly 1 may be attached to a wire guide and encasedwithin a sheath, and then loaded into the catheter for delivery to thetargeted site. A pusher element or another means known to oneskilled-in-the-art is then used to move the filter device assembly 1through the catheter. Upon exiting the catheter, the filter deviceassembly 1 is deployed 115 at the targeted site and allowed totransition to its expanded state.

The stenosis, occlusion, lesion, or other defect in the body vessel canthen be treated 120. Such treatment may include the deployment of astent, a balloon, or other medical device; chemical dissolution; ormechanical thrombolysis, among others. After performing the necessary ordesired treatment, the catheter may be optionally withdrawn 125. Inorder to further enhance the dissolution of embolic material, one ormore thrombolytic drugs or therapeutic agents may be used in addition tothe filter device assembly 1. The various components of the filterdevice assembly 1, or more likely, the stent or other medical deviceused in conjunction with the filter device assembly may, when desirable,be coated with one or more of such drugs. The therapeutic agents mayinclude, but not be limited to, antiproliferative agents,anti-inflammatory agents, and antiplatelet agents, among others.

The delivery catheter used to deliver the filter device assembly 1 maybe made of any material known to one skilled-in-the-art. Such materialmay include but not be limited a polyimide, polyether amide, nylon,polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), andmixtures or copolymers thereof. In its basic form, the catheter is ahollow elongated tube sized to receive the medical device assembly 1.The length of the delivery catheter may be any length necessary ordesired to deploy the filter device assembly 1 at the targeted site inthe vasculature of a patient.

Referring now to FIGS. 3A-3F, the deployment and retrieval of the filterdevice assembly 1 in a body lumen or vessel 7 of a patient is shown. InFIG. 3A the filter device assembly 1 is being delivered into a bodylumen or blood vessel 7 by a delivery tube 29 percutaneously through thevasculature (not shown) of a patient. In this case, the filter deviceassembly 1 is inserted through the proximal end of the delivery tube 29for delivery to a targeted site in the patient, which is downstream fromthe obstruction 19 or the region of the vessel 7 to be treated (e.g.,lesion, etc.) with respect to the direction of blood flow 30.

Referring now to FIG. 3B, during the deployment of the filter deviceassembly 1, the structure 5 begins to expand to its expanded state whenthe structure 5 emerges from the distal end of the delivery tube 29. Asshown in FIG. 3C, the frame 10 of the structure 5 in its expanded stateengages the inner wall 17 of the vessel 7, to anchor the filter device 1at the location of deployment in the vessel 7, thereby, preventing thefilter device 1 from being moved by the blood flowing 30 through thevessel 7 and to ensure that blood does not flow around the device 1 butrather through the filter members 15, 20, 25.

Referring now to FIGS. 3D and 3E, after the filter device assembly 1 isdeployed, either a bare metal or drug eluting stent 37 (FIG. 3D) in anendovascular stenting procedure, a balloon 39 (FIG. 3E) during anangioplasty procedure, or another medical device may be deployed at theobstruction 19. The stent 37 or balloon 39 may expand as shown in FIGS.3D and 3E to interact with the obstruction 19 and to maintain the flowof blood 30 through the obstructed area 19. One skilled in the art willunderstand that other types of treatments may be used to reduce orremove the obstruction, such as the use of lysins for chemicaldissolution, mechanical thrombolysis, or the like, without exceeding thescope of this disclosure. The flow of blood through the filter deviceassembly 1 is maximized by the different porosity associated with thefilter members 15, 29, 25.

Referring now to FIG. 3C, the greater porosity of the first filtermember 15 traps larger particulates or clots arising from theobstruction 19 and/or interaction of the stent 23 with the obstruction19. Particulates that have a diameter smaller than the diameter of theorifices in the first filter member 15 that define the porosity (P₁) ofthe member 15 are allowed to pass through the member 15 along with theflow of blood to the adjacent filter member 25. Some of the particulatesthat pass through the first filter member 15 will become trapped in theadjacent filter member 20. Similarly, particulates that exhibit adiameter smaller than the diameter of the orifices or porosity (P₂)present in the second filter member 20 will pass through the secondfilter member 20 along with the flow of blood. Each additional filtermember allows emboli having a diameter larger than the correspondingporosity, [P₃ . . . P_((2+N))], to be captured and emboli having adiameter smaller than the corresponding porosity, [P₃ . . . P_((2+N))],to pass there through along with the flow of blood to the adjacentfilter member. Any particles that are small enough to pass through thesecond filter member 20 will not cause any detrimental effect on thehealth of the patient.

Referring now to FIG. 3F, upon completion of the treatment of theobstruction 19, the filter device assembly 1 may be removed from theartery or body vessel 7. In this operation, the filter device assembly 1is allowed to transition from its expanded state to its collapsed state.The guide wire upon being coupled to the proximal end of the frame 10(if not already coupled thereto) can pull the collapsed device assembly1 into the catheter 29, wherein the device 1 and subsequently thecatheter 29 may be removed from the body vessel 7.

The foregoing description of various embodiments of the invention hasbeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the preciseembodiments disclosed. Numerous modifications or variations are possiblein light of the above teachings. The embodiments discussed were chosenand described to provide the best illustration of the principles of theinvention and its practical application to thereby enable one ofordinary skill in the art to utilize the invention in variousembodiments and with various modifications as are suited to theparticular use contemplated. All such modifications and variations arewithin the scope of the invention as determined by the appended claimswhen interpreted in accordance with the breadth to which they arefairly, legally, and equitably entitled.

What is claimed is:
 1. A method for providing embolic protection duringtreatment of a stenosis, occlusion, lesion, or other defect in a bodyvessel, the method comprising the steps of: introducing a catheter intothe body vessel; locating an end of the catheter proximate to a targetsite; placing a filter device assembly in the catheter; the filterdevice assembly comprising: a structure having a frame with apredetermined shape, and a distal and proximal portion, the structurehaving frame struts extending from the proximal portion to the distalportion longitudinally along an outside diameter of the filter deviceassembly, the frame struts proximally merging in the proximal portiontoward a reduced diameter and configured to be coupled to a removaldevice; the frame being configured to move between an expanded state forengagement with the body vessel and a collapsed state for delivery andretrieval; and at least a first filter member and a second filtermember, each of the first and second filter members having a proximalpart and a distal part, the proximal part of each of the first andsecond filter members circumferentially attached to the frame struts;the distal part of the first filter member closed such that the firstfilter member forms a first annulus chamber having porosity P₁; thedistal part of the second filter member closed such that the secondfilter member forms a second annulus chamber having porosity P₂; whereinthe magnitude of the porosity for the first and second filter membersfollows the relationship P₁>P₂; deploying the filter device assembly inthe collapsed state into the body vessel past the stenosis, occlusion,lesion, or other defect; and thereafter causing the filter deviceassembly to move from the collapsed state to the expanded state; andtreating the stenosis, occlusion, lesion, or other defect; wherein thefirst and second filter members of the filter device assembly areconfigured such that in the expanded state the first and second filtermembers allow blood to flow there through and to capture emboli in thefirst and second annulus chambers.
 2. The method of claim 1, wherein themethod further comprises the step of withdrawing the catheter from thebody vessel.
 3. The method of claim 1, wherein the filter deviceassembly placed in the catheter further comprises a middle portion, themiddle portion arranged between the distal and proximal portions; and atleast one additional filter member between the first filter member andthe second filter member, each of the at least one additional filtermember a proximal part and a distal part, the proximal part of eachadditional filter member circumferentially attached to the frame struts;the distal part of each additional filter member closed such that eachadditional filter member forms an annulus chamber having a porosity;wherein the magnitude of the porosities of the first filter member, theat least one additional filter member, and the second filter memberdecrease successively from the first filter member toward the secondfilter member with P₁ of the first filter member being the greatest oneof the porosities and P₂ of the second filter member being the smallestone of the porosities.
 4. The method of claim 3, wherein the porosity P₁in the first filter portion of the filter device assembly has openingswith an opening diameter of at least about 150 micrometers; the porosityP₂ in the second filter portion has openings with an opening diameterequal to or less than about 50 micrometers; and the porosity of eachadditional filter member has openings with an opening diameter greaterthan about 50 micrometers and less than about 150 micrometers.
 5. Themethod of claim 4, wherein the first filter member allows emboli havinga diameter larger than the opening diameter of porosity P₁ to becaptured and emboli having a diameter smaller than the opening diameterof porosity P₁ to pass there through along with the flow of blood to anadjacent filter member.
 6. The method of claim 5, wherein the secondfilter member allows emboli having a diameter larger than the openingdiameter of porosity P₂ to be captured and emboli having a diametersmaller than the opening diameter of porosity P₂ to pass there throughalong with the flow of blood.
 7. The method of claim 4, wherein theporosity of each additional filter member is defined by openings with arespective opening diameter and each additional filter member allowsemboli having a diameter larger than the respective opening diameter tobe captured and emboli having a diameter smaller than the respectiveopening diameter to pass there through along with the flow of blood toan adjacent filter member.
 8. The method of claim 1, wherein thetreatment of the stenosis, occlusion, lesion, or other defect includesone selected from the group of the deployment of a stent, deployment ofa balloon, chemical dissolution, or mechanical thrombolysis.